The present invention relates to a valve moving control apparatus having a hydraulic valve phase variable mechanism for altering phase or opening-closing time of at least one of a suction valve and an exhaust valve provided in a cylinder head of an internal combustion engine, particularly to an oil passage system for operating the valve phase variable mechanism.
Hitherto, a valve moving control apparatus for an internal combustion engine having a hydraulic connection changing mechanism has been known (Japanese Utility Model Publication Hei 6-6166). In this connection changing mechanism, in order to change connection and disconnection of a plurality of rocker arms which drive a suction valve or an exhaust valve to open, a changing valve is provided in an oil pressure supply passage.
The oil pressure supply passage leading to an oil pressure supply source has a horizontal passage section in which a small diameter part near the changing valve and a large diameter part connected to the small diameter part through a step are provided. Therefore, even if a relatively large quantity of working oil flows out from the oil pressure supply passage owing to operation of the changing valve, temporary pressure lowering in the oil pressure passage can be restrained by pressure accumulating effect of the large diameter part.
The large diameter part has a function to somewhat decrease pulsation of working oil pressure occurring in the oil pressure supply passage as well as the pressure accumulating function. In order to sufficiently decrease the pulsation of working oil pressure at the large diameter part, it is necessary to further enlarge the diameter of the large diameter part or to lengthen the passage length of the enlarged large diameter part. However, since a supporting section for the rocker shaft and a cooling water passage are formed in the neighborhood of the large diameter part for example, it is difficult to enlarge the diameter of the large diameter part or lengthen the passage length, and therefore the pulsation decreasing function of the large diameter part is limited.